White below the chair rail- use the same white as the trim in a flat finish. It'll be easy to change the bedding colors again in a few years when she's a tween.

Vanessa,

You could also do the light gray below the chair rail. Would stay away from a pink as in a few years she will probably have different favorite colors. White and gray or gray and gray are nice neutrals that allow you flexibility for the future.

Enjoy, you are going to blink a few times and she will be ready to move out of the house. At least it seems that way with one of my daughters moving into her first apartment this past weekend.

Blessings,

Lori

She's only going to be a little girl once though, so I would choose a slightly darker blush for below the chair rail and create a room for her that's as sweet as pie. The short duration of childhood is all the more reason to make it as special as possible and this, after all, is only paint. Love the bedding!